1. Field of the Invention
The present invention relates to an image display control apparatus, more particularly, an image display control apparatus which uses first through third image memories to accomplish predetermined screen effects, and a still picture file reproducing system, which reads out recorded data from a recording medium on which still picture is recorded in a compressed manner or an uncompressed manner and restores it as still picture data.
2. Description of Background Information
Recently, the standardization of high definition still picture disks has been pursued. FIG. 1 presents a block diagram showing the fundamental structure of a system which handles such a disk. Referring to FIG. 1, an image drive unit 1, an audio drive unit 2 and a control drive unit 3 access respective disks on which still picture data, audio data and control data are respectively recorded, and send read-out signals to a player 4.
The still picture data read out by the image drive unit 1 is supplied to the input terminal of a selector 5, which selectively switches the output destination for the input data received at its input terminal to either a compression decoder 6 or a selector 7. The compression decoder 6 has a decoding function with JPEG (Joint Photographic Expert Group: international standards for compression of information of a still picture) base-line compression. The output of the compression decoder 6 is connected to the selector 7. The read-out still picture data is supplied to the compression decoder 6 when it is compressed, and is directly supplied to the selector 7 when it is uncompressed data. The selector 7 serves to selectively switch the output destination for the received data to one of image memories 8a, 8b and 8c.
The image memories 8a to 8c as a whole have a 3-frame structure in order to exhibit predetermined screen effects, and are respectively treated as frame memories each for one frame. The selective switching of those frame memories 8a, 8b and 8c is usually controlled so as to memorize one of three screens: the current (on-the-air) screen, the next screen and the second next screen. The output data of each of the three frame memories is supplied to a screen effect circuit 9 where, when requested by the system, it is subjected to predetermined screen effect control, such as cutting, dissolving, wiping, roll switching, continuous scroll or program wiping that involves data transfer between memories as its premise to the request of the system. The resultant signal is supplied as an image signal to a CRT display 10 as a display device.
Such video reproducing operation is executed in accordance with playback control data read out by the control drive unit 3. That is, the player 4 performs such control as to provide predetermined screen effect in accordance with the playback control data recorded on a disk loaded in the control drive unit 3. The audio data recorded on a disk loaded in the audio drive unit 2 is read out and is then subjected to predetermined signal processing in the player 4, both also in accordance with the playback control data, to thereby drive loudspeakers 11L and 11R. The operation of those individual devices described above is controlled by a control apparatus (not shown).
In this system, the mode is specified by the control data or through a manual operation to accomplish predetermined screen effect control. In the case where one of a first group of screen effect control instructions for accomplishing ordinary or first screen effect control in the predetermined screen effect control is issued, the third frame memory is not required and the first and second frame memories are used. In the case where one of a second group of screen effect control instructions for accomplishing continuous scroll, for example, is issued, the first, second and third frame memories are used. And output image data of those frame memories are selectively output to execute display control corresponding to each screen effect control instruction.
In the case of performing display control on so-called image superimposing, such as chromakey or superimpose, for superimposing one image on another image to form a single image, different from the aforementioned predetermined screen effect control, however, besides the first through third frame memories used to accomplish the predetermined screen effect control, an image memory for holding an image to be superimposed on an image that is produced based on the image data from those three frame memories is needed. Such need of additional memory is undesirable in view of reducing the memory capacity and improving the cost performance.
If the control drive unit 3 is not connected to the player 4 or if no control disk is loaded in the control drive unit 3 even when it is connected to the player 4, this system will not function at all, disabling the reproduction of a still picture.